The invention relates to a tank arrangement and a vehicle with a tank arrangement.
U.S. Pat. No. 4,930,537 discloses a fuel utilization system for a truck having multiple tanks, an above-tank crossover pipe coupling the two tanks. A suction pipe is coupled to a primary tank only. A return pipe is coupled to the crossover pipe.
As an alternative the return pipe can be coupled directly to the primary tank. This method of transferring liquid between the tanks used in this system is commonly known as siphoning. A Venturi device is arranged inside the tank which is flushed when the tank is completely filled.
It is known in the art to use dual tanks for supplying fuel to an engine of a truck. On one hand customers are desirous to have a big tank volume available, on the other hand construction space is very restricted particularly in trucks. As space restrictions do not allow to install one big tank, the tank volume is split in two tanks, e.g. a big master tank and a small slave tank, mounted e.g. on both sides of the frame. The piping between the tanks and the connections to the engine are complex and costly. Often, at least one of the tanks cannot be completely depleted, and refilling of the tanks has to be done in a certain order, i.e. one specific tank has to be filled before the other tank can be filled.
It is desirable to provide a tank arrangement which allows for a better fuel use up and an economic piping between the tanks and the engine. It is also desirable to provide a vehicle with a tank arrangement with a robust level balancing system.
According to a first aspect of the invention, a tank arrangement for a vehicle, particularly a truck, is proposed, comprising at least a first fuel tank and a second fuel tank which are connected by a balancing pipe, a suction pipe for feeding fuel to an engine and a return pipe for feeding fuel from the engine to at least one of the fuel tanks. The balancing pipe is provided with a first end to supply fuel to the first tank and a second end to suck fuel out of the second tank, wherein a check valve is arranged upstream of the return pipe in the balancing pipe between the at least two tanks allowing a flow direction from the second tank to the first tank and blocking a flow in the reverse direction.
Advantageously, the check valve provides an automatic purging function to remove air from the balancing pipe between the first and the second tank. Preferably, the check valve exhibits a low opening pressure corresponding to not more than 100 mm fuel height difference, particularly not more than 500 Pa.
Favourably, the tank arrangement allows for complete emptying of both the master and the slave tank. Of course, more than two tanks can be provided, e.g. one master tank with two or more slave tanks. The suction point of the slave tank can be lowered to the tank bottom which provides a better fuel use up. A specific refilling order is not required. The piping between the tanks and the engine is simplified and cost efficient. Additional interfaces on the tanks can be avoided. Existing tank configurations can be used. The second tank can have a smaller volume as the first tank. Particularly, the tank arrangement provides a robust behaviour for different sizes of return flow from the engine to the tank arrangement.
Particularly, the fuel return pipe can be of smaller diameter than the balancing pipe. Advantageously, the dimensions of the fuel return pipe and the balancing pipe can be adapted to each other to maintain a siphon effect during driving. A skilled person will do this based on parameters influencing the behaviour, such as an injection strength of the return fuel in an ejector pump, flow rate of return fuel and the like.
Further, the connection between the fuel return pipe and the balancing pipe can beneficially be designed such that the fuel entering the balancing pipe flows towards the first tank in which the suction pipe (driven by a fuel pump coupled to the engine) is arranged, thereby maintaining the siphon effect during driving. Most favourably, the system can be designed in a way to ensure that all air is removed from the balancing pipe by means of using the return fuel velocity in the return pipe, an ejector device and the check valve. The system is purging itself automatically also after one of the tanks has been emptied completely. As soon as the tank is refilled, the system can start up automatically again.
The direct fuel pipe connection (balancing pipe) between the second and the first tank can be integrated in a return piping provided for removing fuel from the engine to the tank arrangement by integrating the check valve into the piping and arranging the return pipe accordingly with respect to the check valve. The balancing pipe between the tanks can be increased in diameter compared to a usual return pipe.
According to a favourable development of the invention, the return pipe and the balancing pipe can be merged in an ejector device supporting fuel transport from the second tank to the first tank, wherein the return pipe can be attached to a high pressure side and the balancing pipe can be attached to a suction side of the ejector device. Advantageously, the ejector device sucks the fuel out of the second tank. No fuel can flow back from the engine or the first tank to the second tank. The ejector device allows to keep the fuel level in the second tank slightly lower than in the first tank. This allows to empty the second tank completely without introducing air from the second tank into the first tank. The ejector device can be designed accordingly for keeping a desired level difference in the tanks.
According to a further favourable development of the invention, the check valve can be arranged in a balancing pipe leg inside the second tank. This provides a compact arrangement of the valve. Alternatively, the check valve can be arranged in a balancing pipe portion outside the second tank. The skilled person will choose the proper arrangement according to the actual conditions of the tank arrangement.
According to a further favourable development of the invention, the balancing pipe can have a first portion inside the first tank, a second portion inside the second tank and a third portion connected at a first side to a geodetic top portion of the first tank and at a second side to a geodetic top portion of the second tank.
Advantageously, a standard tank geometry can be used with connection ports at the top of the tank vessel.
According to a further favourable development of the invention, the first tank can provide a suction pipe from the first tank to the engine. Preferably, the engine can be supplied with fuel only by the suction pipe connected to the first tank. As suction of fuel from tank to engine occurs only from the first tank, the second tank can be simplified. The first tank is used as master tank whereas the second tank is used as slave tank.
According to a further favourable development of the invention, the first tank can provide a fuel level sensor for sensing the fuel level in the first tank. Favourably, as suction is only made from the first tank, all return fuel from the engine can be guided into the first tank by the check valve.
According to a further favourable development of the invention, each of the first and second tanks can provide individual air pipes supplying each tank with air independent from the other tank. The tank arrangement becomes more robust as an air connection between the two tanks can be removed. Freezing problems caused by condensed water in a common air connection can be avoided. Alternatively, the first and second tanks can be connected with one common air connection. In this case, only one air filter is necessary.
According to a further favourable development of the invention, the second end of the balancing pipe can have a clearance of not more than 4 cm, preferably not more than 2 cm, to the second tank bottom. Thus, the second tank can be virtually completely emptied thus improving the fuel use up of the tank arrangement.
According to a further favourable development of the invention, the return pipe can join the balancing pipe in a valve unit comprising an ejector device supporting fuel transport from the second tank to the first tank, wherein the check valve and the injector valve can be integrated in the valve unit. Advantageously, at least one of the check valve and/or ejector device can provide quick connections with a snap-in function for attaching and detaching the balancing pipe and/or the return pipe.
According to another aspect of the invention, a vehicle is proposed comprising a tank arrangement for supplying fuel to an engine. A balancing pipe between at least a first tank and a second tank is attached to geodetic upper half portions of the first tank and second tank. The tanks can be of different volumes or exhibit the same volume.
According to a favourable development of the invention, the balancing pipe can be arranged within a web of a vehicle frame.
According to a further favourable development of the invention, only the first tank can be supplied with a suction pipe for providing fuel to the engine. A fuel pump can be installed in the first tank.